Tandem reactions 1,2 -Wittig rearrangements

The l,5-dien-3-ols produced by 2,3-Wittig rearrangement of diallylic ethers can serve as pivotal intermediates for further elaboration through tandem or sequential 3,3-sigmatropic reactions. " The three sequences examined to date are summarized in Scheme 10. 

For instance, the one-pot tandem reaction [2,3]-Wittig-anionic oxy-Cope rearrangement affords the unsaturated aldehydes 571 starting from the bis-allylic ethers 570 at a high level of stereocontrol (equation 224). It was shown that the efficiency of chirality transfer in anionic oxy-Cope rearrangements is determined only by the orientational preference of the oxyanionic bond in the precursors having a single carbinol carbon chiral center . 

Example 4, Tandem Wittig rearrangement/alkylative cyclization reactions ... 

Scheme 2.141. Tandem reaction involving [2,3]-Wittig rearrangement and the Peterson reaction.

Naturally occurring 6-prenylcoumarins have been synthesised from 2-prenyloxy-benzaldehydes through tandem Wittig reaction and Claisen rearrangement. Several of the... 

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